Edward Steichen's post-war 1955 exhibition "The Family of Man" was seen by more than 10 million people and changed the world of photography. Steichen gathered 503 photographs from 273 different photographers around the world at a time when a lot people didn't have access to TVs or magazines. "It was like seeing the world for the first time." Now the exhibition will go back on show in a castle in Luxembourg after nearly three years of renovation.